MIAMI (AP) — By the time Richard Cantlupe received the news of the Connecticut school shooting that left 20 children dead, his students had already gone home for the weekend.

And so the American history teacher at Westglades Middle School in Parkland, Fla., was bracing himself for an onslaught of painful, often unanswerable questions when they returned to class Monday.

"It's going to be a tough day," he said. "This was like our 9/11 for school teachers."

Cantlupe, whose school is about 50 miles north of Miami, and teachers and parents across the country were wrestling with how best to quell children's fears about returning to school for the first time since the massacre at Sandy Hook Elementary School in Newtown, Conn.

School administrators have pledged to add police patrols, review security plans and make guidance counselors available.

And yet, it was pretty near impossible to eliminate the anxiety and apprehension many were feeling.

"For them, you need to pretend that you're OK," said Jessica Kornfeld, the mother of 10-year-old twins in Pinecrest, Fla., a suburb of Miami. "But it's scary."

Connecticut Education Commissioner Stefan Pryor said his agency was sending a letter to school superintendents across the state Sunday evening, providing a list of written prompts for classroom teachers to help them address the shooting in Newtown with their students.

"In many instances, teachers will want to discuss the events because they are so recent and so significant, but they won't necessarily know how to go about it," he said.

Cantlupe said he will tell his students that his No. 1 job is to keep them safe, and that like the teachers in Connecticut, he would do anything to make sure they stay out of harm's way. He is also beginning to teach about the Constitution and expects to take questions on the Second Amendment.

"It's going to lead right into the controversy over gun control," he said.

In an effort to ensure their students' safety and calm parents' nerves, school districts across the United States have asked police departments to increase patrols and have sent messages to parents outlining safety plans that they assured them are regularly reviewed and rehearsed.

Some officials refused to discuss plans publicly in detail, but it was clear that vigilance will be high this week at schools everywhere in the aftermath of one of the worst mass shootings in U.S. history: Twenty-six people were killed at Sandy Hook Elementary School, most children ages 6 and 7. The gunman then shot and killed himself.

Northern Virginia's Fairfax County Public Schools, the largest school system in the Washington area with about 181,000 students, will provide additional police patrols and counselors.

"This is not in response to any specific threat but rather a police initiative to enhance safety and security around the schools and to help alleviate the understandably high levels of anxiety," Superintendent Jack Dale said Sunday.

Dennis Carlson, superintendent of Anoka-Hennepin School District in Minnesota, said a mental health consultant will meet with school officials Monday, and there will be three associates — one to work with the elementary, middle and high schools, respectively. As the day goes on, officials will be on the lookout for any issues that arise, and extra help will go where needed.

"We are concerned for everybody — our staff and student body and parents," Carlson said. "It's going to be a day where we are all going to be hypervigilant, I know that."

In Tucson, Ariz., where a gunman in January 2011 killed six and wounded 12 others, including U.S. Rep. Gabrielle Giffords, the largest school district in the state increased security after Friday's shooting. Planning was under way at the Tucson Unified School District to help teachers and students with grief and fear, and the district was working with Tucson police on security, district spokeswoman Cara Rene said.

In the Chicago Public Schools, the nation's third-largest school district, officials said they would reiterate their existing safety and emergency-management plans to keep more than 400,000 students safe, and deploy police or counselors to schools as needed.

"With this incident, we took it as an opportunity to remind all of our principals to review and refresh their individual emergency-management plans and remind staff of standard safety protocol," said Chief Safety and Security Officer Jadine Chou.

Many schools will be holding a moment of silence Monday and will fly flags at half-staff.

Meanwhile, at home, many parents were trying their best to allay their children's fears while coping with their own. Kornfeld said her town is a lot like Newtown: a place where people generally feel safe being at home without the doors locked and playing outside after school.

"Why would that happen there?" she said. "It kind of rocks everything."

She sat down with her son and daughter after school Friday and explained to them what had happened. She reminded her children that they were with her, and safe.

"But it could have been us," her son replied.

Hoping to reassure them, she drove the children to their elementary school over the weekend. She wanted them to know it was still a safe place.

"Our school is the same as it was when you left," she told them. "It's going to be fine."